Conventional oscillator circuits are designed so that they will start oscillating (“start up”) and that their respective amplitude will be controlled. For a linear circuit to oscillate, it must meet the “Barkhausen conditions,” that is, the loop gain must be one and the phase around the loop must be an integer multiple of 360 degrees. In practice, the loop gain is initially larger than unity. Random noise is present in all circuits, and some of that noise will be near the desired frequency. A loop gain greater than one allows the amplitude of frequency to increase exponentially each time around the loop. With a loop gain greater than one, the oscillator will start. However, with a loop gain of greater than one, significant harmonic distortion is introduced, and the frequency stability of the oscillator may be affected.
A Wien bridge oscillator is a type of electronic oscillator that generates sine waves under a large range of frequencies. The Wien bridge oscillator is typically based on a bridge circuit comprising comprises four resistors and two capacitors (see FIG. 1). In use, the oscillator can operate as a positive gain amplifier combined with a band pass filter that provides positive feedback. In certain applications, such as power applications, Wien bridge oscillators may be used as inputs for circuit control and/or voltage reference (e.g., for power inverters). However, the quality of the sine wave produced by conventional Wien bridge oscillators is often subject to noise and distortion, and is not able to effectively simulate or approximate a true (or “pure”) sine wave.